Delay in downloading email and missing graphics, pictures and logos

[#1]

Yes.  The 3 Apple devices with the same Mail loading issue are all connected by WiFi on 5 GHz.  My iPhone 15 is also connected by WiFi on 5 GHz and is not giving me any problems. 

[#2]

Yes I’ve done this.  Will try again though. 

[#3]

Friend’s devices are connected to 5 GHz band by WiFi    You are correct that thermostats, bird box and very old printers are connected to 2.4 GHz.  Yes I have checked what is connected where.   The 3 Apple devices giving problems are all connected by WiFi on 5GHz band   I have 19 devices connected in total. 12 by WiFi, 7 by Ethernet.   3 are on 2.4 band (bird box, thermostats, old printer) all by WiFi.  Rest on 5 GHz band

[#4]

@Natsand like John I'm at a bit of a loss then.

It seems to be just the Apple devices and TBH I have little experience of them but what I do recall, is that they have a propensity to use encrypted DNS ( DNS over https or DNS over TLS). That might be an avenue worth exploring...

[#5]

@Natsand Which version of the OS (IOS) does each device use? I wonder if all that have problems use the same version and all that don't have issues are using another version.

Have you also tried changing the DNS on the non-working devices to something like 8.8.8.8? Or if they are set to that, clear it so it uses the DNS provided by the plusnet router? 

[#6]

Hi Dabbler

Thanks for your response.  All iOS devices are on 26.4.    Since first logging this problem last week my iphone15 is now behaving the same as the other 3. 

It would appear to be isolated to the Mail App.  Anyone coming into my house and using both the WiFi AND the Mail app are affected.  If using Outlook or other then they are fine.   I have deleted the Mail App altogether on one iPad and reinstalled it to see if it will cure the problem but it doesn’t so haven’t tried it on the other devices.   For the moment I am accessing emails using the GMail App.  When I check the emails on there against the Mail App I can see there is a time delay in coming into the Mail App and when opening them still a delay and graphics/photos logos missing in Mail.  

My ‘configure DNS setting for my WiFi says it is Automatic?